Save the yeast!

My night-before-brew-day (Brew Day Eve?) ritual consists of a) weighing and grinding the grain for the mash, b) preparing the yeast slurry, if necessary, and c) setting out the first stage equipment. I mentioned the yeast preparation briefly in last week’s recipe, Mortal Sin, and promised to divulge my secrets for re-using and re-culturing yeast.

If you brew, you know that the right yeast strain can make the difference between a good beer and a great one. There are, in fact, certain beers that cannot be brewed without the correct yeast. Anchor Steam depends on a very specific warm-tolerant lager yeast; Belgian Trappist beers would just not work without a traditional high-alcohol tolerant strain; in trying to clone Dieu Du Ciel’s Mortal Sin last week, we went to great pains to capture and reuse the yeast found in their bottles.

The other thing about “the right yeast” is that it can get expensive. Fresh liquid yeast costs anywhere from $5 to $8 in the home brew shop. But if you can save it, re-use it, you cut the cost down. Tomorrow I will be brewing a Munich Dunkel lager, using the same Southern German Lager yeast from White Labs that I used to brew my delicious Munich Hell, Vienna Lager, Bock and Rauchbock over the last few months. Yup, using the same yeast, for the fifth time. Here’s how I do it. Caution: some purists, some much more scientific types, will cringe, shudder and scream at the computer screen as they read this. I know, this shouldn’t work this easily. But it does, it has, and I have no qualms about sharing my dirty little secret.

Yeast in Sanitized Milk Bottle
Yeast in Sanitized Milk Bottle

It starts on the day I rack a beer from primary to secondary. If the beer to be racked was brewed with a yeast I know I am planning to reuse soonish (within the next couple months, generally), and if the initial fermentation has gone well, as far as I can tell, I sanitize a glass pint-sized milk bottle. After racking the beer into the carboy, I scoop out, with a sanitized measuring cup, a cup or so of the dregs. These dregs consist of malt proteins, hop debris, and hopefully a fair amount of yeast cells. These dregs are poured carefully into the pint bottle, a solid rubber stopper is affixed, and the sample goes into the fridge.

Close up of Yeast
Close up of Yeast

A day or two before I will be brewing with the saved yeast, I sanitize a glass quart-sized milk bottle. I boil a cup of water with two tablespoons of dry malt extract for about 5 minutes. This wort is cooled to 70 – 75°F, poured into the sanitized quart bottle, and the saved yeast dregs are poured carefully into the cool wort. A little swirling to mix, and a stopper with an airlock is put on the bottle. I let it work for 12 hours or so, and if brewing is still a ways off I might “feed” the yeast again with another 1/2 cup of water boiled with 1 tablespoon of DME, chilled of course. Voilà, on Brew Day I have a cup and a half or two cups of active yeast slurry, ready to pitch.

In the case of a commercial yeast captured from a bottle, this process takes place a little at a time over several days, with a gradual slow build-up of a quarter to a half-cup at a time.

So, my Southern German Lager yeast is just beginning to foam and bubble, two hours after pitching, and should be ready to pitch in my Munich Dunkel in about 13 hours. See you then!

Timing Is Everything – Racking and Bottling

One of the most frequently asked questions from customers in the Market is “When?” When should I rack to secondary? When should I bottle? When can I try a bottle to see if it’s ready to drink?

Not an easy question to answer, in many cases. It depends on a variety of factors: style of beer, strength of beer, yeast used in fermentation, temperature of the brewing and fermenting environment; even convenience affects the answer.

Simplified, in my home brewery, all things going well and as planned (which is rare, I must admit), here is my normal schedule.

  • Brew Day minus 1: weigh and crush grains, prepare yeast culture if necessary, double-check recipe for all ingredients.
  • Brew Day: brew, start fermentation.
  • Brew Day plus 2 or 3: if fermentation has not visibly started, open and check seals, etc… if necessary, re-pitch yeast or take other remedial actions…
  • Brew Day plus 8 – 10: rack to secondary. This lines up nicely with my schedule: I brew on Thursday, and rack on either Sunday or Tuesday (both of which are days I do not currently work). This is generally true for all styles, ale or lager, moderate strength or strong.
  • Racking Day plus 12 – 15 (for moderate strength ales): bottle.
  • Racking Day plus 30 – 40 days (for lagers and/or high-gravity beers): bottle.
  • Bottling Day plus 6 – 8 (for moderate strength ales): taste test.
  • Bottling Day plus 14 – 16 (for lagers): taste test
  • Bottling Day plus 21 (for high gravity beers): taste test.

The taste test will tell you a) if the carbonation is adequate for drinking, and b) if the beer needs more aging for flavor purposes.

One of the indicators of a beer’s readiness for transfer to the secondary is the airlock. If there is still frequent bubbling (say more than 4 or 5 bubbles per minute) it’s probably best to wait a few more days. If it was bubbling regularly and has slowed down to a bubble every 20 or 30 seconds it is fine to rack it. All bubbling should have ceased in the secondary before you think about bottling, and if you are using a glass carboy as your secondary, you should see a nearly clear beer. If fermentation activity is ongoing in the secondary, or if it has not clarified, it’s probably best not to bottle it yet.

A word about shelf life – both hops and alcohol are natural preservatives, therefore a stronger beer or a hoppier beer will last longer; a weaker beer or one that is less hoppy will go stale sooner. Altbiers, Kölsch, Pilsners, Pale Ales and Brown Ales generally need to be consumed within 4 – 6 months. Old Ales, Barleywines, Belgian Dubbels and Tripels, Bocks and Imperial Stouts can last and indeed improve with age, up to 18 months or more.

I was reminded of this tonight when I opened a Belgian Tripel which I brewed way back in February 2009. It was bottled in April, and I tried it for the first time in June. I was not impressed at that point. It looked nice, clear and pale golden color, big white head, etc. but the aroma and taste were harsh. Way too much alcohol in the nose and the flavor, not enough of the yeast-based esters that I expected (my favorite Trappist Tripels have both an aroma and a flavor that remind me of pistachios or almonds). I was disappointed, but I did not dump the bottles, instead allowing them to rest peacefully in the dark. Now, I have about 6 bottles left of what has become a delightful strong golden ale with lots of Belgian yeast character. I suspect it will get even smoother and more delightful over the next couple months if I can restrain myself from drinking it too soon.

Additionally, I was bottling a bock at the same time. It was brewed the day after Thanksgiving and has been lagering for five weeks. It tasted pretty smooth and malty as I bottled it, but time will tell. I hope to be able to hold off and not even taste it until at least February, but we shall see. It will be fully ready, if all goes well, around the time I begin sugaring the first weekend in March, and improve and be even better for summer barbecues. I may even try to save a couple bottles for the last day of summer in September.

A Bitter Subject – Hops, aau’s, IBU’s, HBU’s…?

Caution: technical stuff and math follow!

What do you think when you see a beer recipe that calls for hops measured not in ounces but in HBU’s? or when you read a label and it tells you the beer has so many IBU’s? Ever notice on that packet of hops you bought at the Home Brew Store that the hops are rated based on aa%? What gives? How do you figure out how much to use? It’s not as complicated as it looks at first blush.

AAU’s and aa%: The relative bitterness of a given crop of hops is measured based on the acidity of the flower. The acid that brewers are primarily concerned with is the “alpha acid”, or aa – this is measured in a percentage, hence aa%. The higher the number, the more acidic and thus the more bitter the hop. The Hallertau I used this morning measured 3%, the Perle 6%, so the Perle were twice as bitter as the Hallertau. An AAU (alpha acid unit) is the product of the percentage of bitterness times the amount used – 1 ounce of those 3% Hallertau provides 3 AAU’s, one ounce of the Perle provides 6 AAU’s.

More common and relevant to the homebrewer is the HBU – Homebrewer’s Bitterness Unit – but it’s exactly the same thing as an AAU. If your recipe calls for 6 HBU’s of a given hop, work backwards. If you have a Chinook hop at 12% aa, you need to use 1/2 oz. to get 6 HBU’s (or AAU’s) – right?

IBU’s – International Bitterness Units – are the result of using the hop. There is actually an esoteric table which gives an indication of how bitter a beer will be based on how much of which hops are boiled, and for how long. So IBU’s are the sum total of all the hops added in a given beer, multiplied by a factor depending on length of boil and volume and strength of the wort. For more information on this, I recommend the excellent discussion in Greg Noonan’s “New Brewing Lager Beer”.

In a nutshell, the average homebrewer can use the following simplified tables, which I used in “North American Clonebrews”, although it is based on a table Greg devised for the “Seven Barrel Brewery Brewers’ Handbook”.

Assuming moderate/average strength wort, in a 5-gallon boil:

  • 0 minutes, or dry-hopping – .7
  • 5 minutes – .7
  • 15 minutes – 1.25
  • 20 minutes – 1.5
  • 30 minutes – 2.4
  • 45 minutes – 4.0
  • 60 minutes – 4.25
  • 90 minutes – 4.5

So one would multiply the HBU’s (aa% times ounces) times the above factors, to get the IBU’s.

If one boiled only one ounce of a 4.5% aa hop for 60 minutes, one would have 19.1 IBU’s (4.5 x 4.25)

But if one also boiled one ounce of a 2% aa hop for 5 minutes one would end up with 20.5 IBU’s (add another 1.4, or 2 x .7).

So work backwards – if you know the approximate IBU rating you are shooting for, it is relatively easy to calculate the amount of hops, the desired aa%, and the length of boil. At least I think it is…

Looking at the recipe I posted earlier for the Dortmund Export, we see a total of 22.5 IBU’s. 3.2 of that came from the first addition of Hallertau (.25 x 3 x 4.25); 12 from the 45-minute addition of Perle (.5 x 6 x 4); 5.4 from the second batch of Hallertau (.75 x 3 x 2.4) and the last 1.9 from the final addition of Hallertau (.5 x 3 x 1.25).

So a quick quiz: If you boil 1/2 oz. of Galena at 8% aa for 90 minutes, 1 oz. Tettnang at 4% for 45 minutes, and dry hop with 1 oz. Saaz at 5%, how many IBU’s will the beer have? (Answer follows)

.5 x 8 x 4.5 = 18; 4 x 4 = 16; 5 x .7 = 3.5; total 18 + 16 + 3.5 =37.5 IBU’s.